Low embodied energy concrete mixture

ABSTRACT

A method for making a low embodied energy cementitious mixture by blending a variety of post-consumer wastes, post-industrial wastes, as well as renewable, organic and recyclable materials with Portland cement or a material having similar cementitious properties. The primary materials are recycled concrete, coal-fired fly ash waste, silica fume, post-industrial waste, organic or inorganic waste fibers. Glass, brick, ceramics, ground tires and other waste products can also be included.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit to provisional application No.61/048,800, filed Apr. 29, 2008, which is incorporated by referenceherein in its entirety.

FIELD OF THE INVENTION

A method is described for making a low embodied energy cementitiousmixture by blending a variety of post-consumer wastes, post-industrialwastes, as well as renewable, organic and recyclable materials withPortland cement or a material having similar cementitious properties.The primary materials are recycled concrete, coal-fired fly ash waste,silica fume, post-industrial waste, organic or inorganic waste fibers.Glass, brick, ceramics, ground tires and other waste products can alsobe included. No virgin gravel or sand is used in the describedcementitious mixture.

BACKGROUND

Concrete is one of the most ubiquitous materials found in the modernworld. It is one of the primary materials used to build almost everydurable structure, large or small, comprising our cities and towns,including: sidewalks; roads; bridges; retaining walls; skyscrapers;building foundations; sewers; and hundreds of other structures. Inshort, concrete is used in every corner of the Earth and our way of lifedepends on its continued use.

Although concrete can be made in many ways with many additives andvarious methods for its creation and use, it is generally made with fourparts gravel, two parts sand, one part Portland cement and water. Theseingredients are mixed, poured into forms and allowed to set. Thisprocess has been repeated thousands of times every day for decades anddecades.

Unfortunately, the manufacture of concrete's constituent parts createsan enormous amount of environmental havoc, which must be addressed. Hugequantities of sand, limestone and gravel must be mined or dredged eachyear to satisfy the requirements of concrete manufacture. Theseprocesses scar the Earth and must be performed using large machines,which burn a tremendous amount of fossil fuels, which also contribute toglobal warming. However, the carbon dioxide created by these processespales in comparison to that required to manufacture Portland cement. Themanufacture of one pound of Portland cement creates almost one pound ofcarbon dioxide due mostly to the decarbonation of limestone and the fuelburned to heat kilns to the required temperature of nearly 1500 degreesCelsius. International studies have shown that the manufacture ofconcrete leads to 5-8% of total CO2 emitted worldwide.

To be more cost effective and to prevent excessive waste, concretemixtures have been developed which use recycled materials to reduce anyunnecessary environmental impacts. Recyclable materials exist in manymanufacturing industries such as coal-generated electricity, variousmetal purification processes, silica production and cement and limekilns to name a few. These mixtures generally consist of either theaddition of an aggregate mixture, made of recycled concrete or theaddition of fibers, such as plant fibers, carpet fibers, or rubberfibers. The recyclable materials that can be used in the concretemixtures exist in many manufacturing industries such as coal-generatedelectricity, various metal purification processes, silica production andcement and lime kilns to name a few.

What is needed is a concrete mixture that uses all of the commonlyavailable types of recycled materials, thus requiring little or noPortland cement, and full recycled aggregate replacement to reducelandfill and destruction of our natural resources. Additionally, theconcrete formed must have comparable strength, viscosity, and othercharacteristics comparable to that of standard concrete created fromvirgin materials.

SUMMARY OF THE INVENTION

It is an aspect of the present inventive concept to provide for a lowembodied energy concrete mixture that comprises the minimal amount ofvirgin materials and requires little or no Portland cement. Variousaspects of the invention described herein may be applied to theparticular instances set forth below or for a variety of other kinds ofmaterials. It shall be understood that different aspects of theinvention can be appreciated individually, collectively or incombination with each other. While the new methods described herein maybe in conjunction with the manufacture of concrete that can range fromsmall to bulk quantities, it shall be understood that these methods canbe applied and used to manufacture other concrete-based buildingmaterials such as roof tiles, deck tiles, floor tiles, cement boards,masonry blocks, and other similar building materials.

The above aspect can be obtained by a concrete mixture comprised of anaggregate composed of recycled concrete and a cement portion made up aminimal amount of Portland cement, as well as fly ash and ground blastfurnace slag. The cement portion of the mixture comprises no more than5% Portland cement, the bulk being made of recycled materials.

The above aspect can also be obtained through the addition of fibrousrecycled materials to the aggregate and cement portions to increase thecrack-resistance of the concrete. The fibrous material may bemanufactured using recycled, finely-ground, tires, carpet, or waste ricehulls. The above aspect can also comprise recycled glass, and recycledE-glass.

The above aspect can also be obtained through the addition of silicafume, a waste product from steel production, or cement and lime kilndust, waste products of the cement and lime industries respectfully, tothe aggregate and cement portions with or without the addition of thefibrous materials. The addition of silica fume to the mixture increasesthe strength and reduces the water penetration, protecting steelreinforcements. The addition of cement or lime kiln dust to the mixtureincreases the strength and regulates the reaction timing, including setand curing speed.

In one aspect, a mixture of these materials can be created with theobject of using the least amount of energy to create a given unit ofconcrete.

In another aspect, a mixture of these materials can be created with theobject of using the least amount of energy while creating a concretewith a compressive strength in excess of 3000 p.s.i.

In another aspect, a mixture of these materials can be created with theobject of using the least amount of energy while creating a concretethat has manufacturing costs similar to that of ordinary concrete.

In another aspect, a mixture of these materials can be created with theobject of using the least amount of energy while creating a low slump,flowable concrete.

These, together with other aspects and advantages, which willsubsequently become apparent, and reside in the details of constructionand operation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawing forming a part hereof, whereinlike numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram representing a method for creating a lowembodied energy concrete mixture according to an embodiment.

DETAILED DESCRIPTION

The following detailed description of embodiments of the invention isillustrative only and not limiting. Other embodiments will be obvious tothose skilled in the art in view of this description.

The novel process described in the exemplary embodiments for themanufacture of low embodied energy concrete is intended to be read inconnection with the accompanying drawings, which are to be consideredpart of the entire written description.

Reference will now be made in detail to the presently preferredembodiments of the invention, examples of which are illustrated in theaccompanying tables, wherein like reference numerals refer to likeelements throughout.

In one embodiment, the present invention relates to a cementitiousmixture which can comprise ground granulated blast furnace slag (GGBFS),fly ash of various grades, silica fume, recycled concrete, brick andother similar building materials, ground recycled carpet fiber, whichcan include nanoparticles, rice hulls and other organic fiber containingmaterials, and water. Portland cement is well known in the art and isthe most common type of cement in general use, as it is a basicingredient of concrete, mortar, stucco and most non-specialty grout.

FIG. 1 is a flowchart illustrating an exemplary method of implementing amethod to create a cementitious mixture, according to an embodiment.

The method can begin with operation 100, wherein an operator creatingthe mixture provides ingredients which can comprise Portland cement(and/or GGBFS, lime kiln dust, cement kiln dust), fly ash, silica fume,recycled aggregate, ground recycled carpet fibers, organic fibers(and/or high range water reducer), and water. Any of these ingredientscan be optional, and additional ingredients can be added (e.g., highrange water reducer, such as polycarboxylate or super plasticizer.)

In operation 102, the operator mixes the ingredients provided inoperation 100. The ingredients can be mixed using any mixing equipmentknown in the art. For example, a drum mixer, pan mixer, or wheel barreland shovel.

In an embodiment, a low energy content, cementitious mixture capable ofreplacing a typical 4:2:1 concrete mixture, in terms of compressivestrength and slump properties, can be created using 4% to 6% Portlandcement, 6% to 8% fly ash of any type, 2% to 4% silica fume as measuredas a percent of the amount of Portland cement utilized, 2500 to 3600pounds per cubic yard of recycled concrete, bricks or other recycledbuilding materials per cubic yard of cementitious mixture created, 2.5to 3.5 pounds per cubic yard of recycled carpet fibers furthercomprising nanoparticles, 5.5 to 6.5 pounds per cubic yard of rice hullwaste fibers, and a 30% to 65% ratio (by weight) of water to thecombined weight of Portland cement and fly ash used.

In a second embodiment, an extremely low energy content, cementitiousmixture can be created using 0% to 2% Portland cement, 3% to 4% GGBFS,6% to 8% fly ash of any type, 2% to 4% silica fume as measured as apercent of the amount of Portland cement utilized by weight, 2500 to3600 per cubic yard pounds of recycled concrete, bricks or otherrecycled building materials per cubic yard of cementitious mixturecreated, 2.5 to 3.5 pounds per cubic yard of recycled carpet fibersfurther comprising nanoparticles, 5.5 to 6.5 pounds per cubic yard ofrice hull waste fibers, and a 30% to 65% ratio (by weight) of water tothe combined weight of Portland cement and fly ash used.

In a third embodiment, a low energy content, cementitious mixture,having a compressive strength greater than 8,000 p.s.i. can be createdusing approximately 5.5% Portland cement, approximately 8% fly ash ofany type, approximately 15% silica fume as measured as a percent of theamount of Portland cement utilized by weight, 2500 to 3600 pounds percubic yard of recycled concrete, bricks or other recycled buildingmaterials per cubic yard of cementitious mixture created, 2.5 to 3.5pounds per cubic yard of recycled carpet fibers further comprisingnanoparticles, 5.5 to 6.5 pounds per cubic yard of rice hull wastefibers, 1.25% to 1.75% high range water reducer measured as a percent ofthe amount of Portland cement utilized by weight, and a 25% to 65% ratio(by weight) of water to the combined weight of Portland cement and flyash used.

In a fourth embodiment, a low energy content, cementitious mixture,having high flowability properties can be created using 4.5% to 5.5%Portland cement, 6% to 8% fly ash of any type, 2% to 4% silica fume asmeasured as a percent of the amount of Portland cement utilized byweight, 2500 to 3600 pounds per cubic yard of recycled concrete, bricksor other recycled building materials per cubic yard of cementitiousmixture created, 2.5 to 3.5 pounds per cubic yard of recycled carpetfibers further comprising nanoparticles, 5.5 to 6.5 pounds per cubicyard of rice hull waste fibers, 1.25% to 1.75% high range water reducermeasured as a percent of the amount of Portland cement utilized byweight, and a 20% to 65% ratio (by weight) of water to the combinedweight of Portland cement and fly ash used.

Different Applications and Use of Post-Industrial Waste Like Materials

Several U.S. patents have described the use of some of theaforementioned post-industrial waste in the development of cementitiousapplications. It shall be understood that any of the waste componentsdisclosed in the following patents, which are all incorporated byreference in their entirety, may be utilized with various aspects of theinvention herein. For example, U.S. Pat. No. 5,435,843 discusses acement composed of type C fly ash and an alkali metal activator formortar and concrete applications. U.S. Pat. No. 4,997,484 requires thesame with the addition of citric acid. In both patents there is noconsideration of post-industrial wastes other than type C fly ash ormention of fine and course aggregate either virgin or of recyclednature. U.S. Pat. No. 5,714,003 expands the scope to use anysub-bituminous fly ash, and requires potassium carbonate, citric acidand retarding agent for general cement applications, but again containsno mention of other post-industrial wastes or the use of recycledaggregates. U.S. Pat. No. 5,084,102 considers another post-industrialwaste, blast furnace slag, as an ingredient for a ready-to-use drypowder that when combined with water can be used in concreteconstructions, products or parts, but without consideration of loweringthe embodied energy of concrete by using recycled aggregates or otherpost industrial waste sources.

The resulting low embodied energy concrete products herein may depend onthe naturally occurring remaining composition of industrial processingof mined raw materials to form a self-hardening reaction. When harnessedeffectively, hydration will initiate a self-hardening reaction withinthese “waste” materials. Because low embodied energy concrete mayincorporate by-products that are not manufactured for specific chemicalcomposition or further industrial use, each source can have a uniquemakeup when compared to other sources of the same material. Thus it ispreferable or often times necessary to optimize with the specificchemical composition of each unique source for the best or desiredcombination of waste materials in wallboard end products.

The typical compositions of considered post-industrial waste materialsfollow, however these ranges are not representative of all wastematerial sources that may be considered useful in the low embodiedenergy concrete:

Fly Ash Type C

Component Percentage SiO₂ 15-60 Al₂O₃ 10-30 Fe₂O₃  4-15 CaO  5-40 MgO 1-10 SO₃  0-10 Na₂O 0-6 K₂O 0-4 LOI 0-5Fly Ash Type F

Component Percentage SiO₂ 20-60 Al₂O₃  5-35 Fe₂O₃ 10-40 CaO  1-12 MgO0-5 SO₃ 0-4 Na₂O 0-4 K₂O 0-3 LOI  0-15Blast Furnace Slag

Component Percentage SiO₂ 27-38 Al₂O₃  7-12 Fe₂O₃ or FeO 0.2-1.6 CaO34-43 MgO  7-15 MnO 0.15-0.76 S   1-1.9Steel Slag

Component Percentage SiO₂ 10-19 Al₂O₃ 1-3 Fe₂O₃ or FeO 10-40 CaO 40-52MgO  5-10 MnO 5-8 S   0-0.1 P₂O₅ 0.5-1   Metallic Fe 0.5-10 Lime Kiln Dust

Component Percentage CaO (free) 17-25 CaO 56-60 MgO 1.1-4.9 SiO₂  8-17Al₂O₃, Fe₂O₃,   5-5.5 MnO, TiO₂, P₂O₃ CO₂ 13-18 LOI 14-23Cement Kiln Dust

Component Percentage Ca₂CO₃ 30-60 SiO₂ 10-20 Al₂O₃ 2-6 Fe₂O₃ or FeO 1-4CaO  5-40 MgO 1-4 Na₂SO₄ 1-3 CaSO₄ 2-8 K₂SO₄ 3-9 KCI 1-3 KF 0.1-1  

Although the invention has been described in terms of exemplaryembodiments, it is not limited thereto. Rather, the appended claimsshould be construed broadly, to include other variants and embodimentsof the invention, which may be made by those skilled in the art withoutdeparting from the scope and range of equivalents of the invention.

1. A cementitious mixture comprising: Portland cement; fly ash; silica fume; recycled aggregate; ground recycled carpet fibers; organic fibers; and water.
 2. The cementitious mixture described in claim 1, wherein the ground recycled carpet fibers comprise nanoparticles.
 3. The cementitious mixture described in claim 1, wherein the recycled aggregate comprises crushed, recycled concrete.
 4. The cementitious mixture described in claim 1, wherein the recycled aggregate comprises recycled glass.
 5. The cementitious mixture described in claim 1, wherein the recycled aggregate comprises crushed concrete and bricks.
 6. The cementitious mixture described in claim 1, wherein the Portland cement comprises between zero percent (0%) and ten percent (10%) of the mixture as measured by weight.
 7. The cementitious mixture described in claim 1, wherein the organic fibers are rice hulls and other natural waste fibers.
 8. The cementitious mixture described in claim 1, wherein ground granulated blast furnace slag is substituted for some of the Portland cement.
 9. The cementitious mixture described in claim 8, wherein the Portland cement comprises between zero percent (0%) and seven percent (7%) of the mixture as measured by weight.
 10. The cementitious mixture described in claim 8, wherein the ground granulated blast furnace comprises between three percent (3%) and seven percent (7%) of the mixture as measured by weight.
 11. The cementitious mixture described in claim 8, wherein the organic fibers are rice hulls or other natural waste fibers.
 12. The cementitious mixture described in claim 1, wherein lime kiln dust is substituted for some of the Portland cement.
 13. The cementitious mixture described in claim 12, wherein the Portland cement comprises between one percent (0%) and seven percent (7%) of the mixture as measured by weight.
 14. The cementitious mixture described in claim 12, wherein the ground granulated blast furnace comprises between three percent (0%) and seven percent (7%) of the mixture as measured by weight.
 15. The cementitious mixture described in claim 12, wherein the organic fibers are rice hull waste fibers.
 16. The cementitious mixture described in claim 1, wherein cement kiln dust is substituted for some of the Portland cement.
 17. The cementitious mixture described in claim 16, wherein the Portland cement comprises between zero percent (0%) and seven percent (7%) of the mixture as measured by weight.
 18. The cementitious mixture described in claim 16, wherein the ground granulated blast furnace comprises between three percent (3%) and seven percent (7%) of the mixture as measured by weight.
 19. The cementitious mixture described in claim 16, wherein the organic fibers are rice hull waste fibers.
 20. A cementitious mixture comprising: Portland cement; fly ash; silica fume; recycled aggregate; ground recycled carpet fibers; organic fibers; high range water reducer; and water.
 21. The cementitious mixture described in claim 20, wherein the Portland cement comprises between zero percent (0%) and three percent (10%) of the mixture as measured by weight.
 22. The cementitious mixture described in claim 20, wherein the organic fibers are rice hulls or other natural waste fibers.
 23. A method to create a cementitious mixture, the method comprising: providing the following ingredients: Portland cement; fly ash; silica fume; recycled aggregate; ground recycled carpet fibers; organic fibers; and water; and mixing the ingredients.
 24. The method to create a cementitious mixture as recited in claim 23, wherein high range water reducer is comprised in the ingredients. 